The present invention relates to an improvement in a vane pump which is used for a supercharger, a compressor, and the like.
A vane pump schematically shown in FIG. 5 has been heretofore widely known.
In FIG. 5, reference numeral 31 designates a housing; 32, a rotor inserted eccentrically into an inner peripheral space of the housing 31 and rotatably supported by a rotational shaft 33; 35a, 35b and 35c, plate-like vanes disposed radially retractably from vane grooves 34a, 34b and 34c equally spaced apart so as to peripherally divide the outer peripheral side of the rotor 32 into three sections. When the rotor 32 is rotated in the direction as indicated by the arrow X by the rotational shaft 33, the vanes 35a, 35b and 35c are moved out in the direction of the outside diameter by the centrifugal force, and the end edges thereof rotate while slidably contacting the inner peripheral surface of the housing 31. Since the rotor 32 is eccentric with respect to the housing 31 as previously mentioned, as such rotation occurs, volumes of working spaces 36a, 36b and 36c defined by the housing 31, the rotor 32 and the vanes 35a, 35b and 35c are repeatedly enlarged and contracted. In the figure, the working space 36a gradually enlarges its volume s the rotor rotates to suck therein a fluid from an intake port 37 axially bored; the working space 36c gradually contracts its volume as the rotor rotates to discharge a fluid to an outlet port 38 bored axially thereto. It is known that the intake port 37 and outlet port 38 are designed so that both the ports axially extend from the side wall of the housing 31 as shown, and that they extend externally from the peripheral wall of the housing 31.
However, in the above-described conventional example, the fluid having been sucked axially from the intake port 37 rotatively flows along the inner peripheral surface of the housing 31 within the pump and again changes its direction of flow into the axial flow at the outlet port 38. therefore, the kinetic energy, specifically the inertia of the fluid obtained by the rotation of the vanes 35a, 35b and 35c does not effectively act in the discharge direction. Also, n the case where both the intake port 37 and outlet port 38 are extended externally from the peripheral wall of the housing 31, the centrifugal force effectively acts during the stage of the discharge whereas the centrifugal force functions as resistance by which the suction force is attenuated. Accordingly, it is difficult to accelerate the flow of fluid. An amount of leakage of fluid from the working space 36a to 36c, from 36b to 36a, and from 36c to 36b between the vanes 35a, 35b and 35b and the housing 31 increases, which unavoidably deteriorates the efficiency of volume.